Cellulose-based substrates encapsulated with polymeric films and adhesive

ABSTRACT

A cellulose based substrate ( 20 ) generally includes a cellulose based sheet having a corrugated medium ( 48 ) spanning between first and second linerboards ( 44  and  46 ), wherein the corrugated medium includes at least one sizing agent for moisture wicking resistance. The cellulose based substrate further includes a polymeric film ( 43 ) encapsulating at least a portion of the cellulose based sheet.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 10/879,846, filed on Jun. 29, 2004, the disclosureof which is hereby expressly incorporated by reference.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to cellulosebased substrates encapsulated with polymeric films.

BACKGROUND

Containers made from fibreboard are used widely in many industries. Forexample, fibreboard containers are used to ship products that are moistor packed in ice such as fresh produce or fresh seafood. It is knownthat when such containers take up moisture, they lose strength. Tominimize or avoid this loss of strength, moisture-resistant shippingcontainers are required.

Moisture-resistant containers used to date have commonly been preparedby saturating container blanks with melted wax after folding andassembly. Wax-saturated containers cannot be effectively recycled andmust generally be disposed of in a landfill. In addition, wax adds asignificant amount of weight to the container blank, e.g., the wax canadd up to 40% by weight to the container blank.

Other methods for imparting moisture resistance to container blanks haveincluded impregnation with a water-resistant synthetic resin or coatingthe blank with a thermoplastic material. In the latter case, formingwater-resistant seals around container blank peripheral edges and edgesassociated with slots or cutouts in the container blank has been anissue. When seals along these edges are not moisture resistant or fail,moisture can be absorbed by the container blank with an attendant lossof strength. In addition, obtaining consistent and reproducible bondingof the thermoplastic material to the container blank and around edgeshas been a challenge.

Faced with the foregoing, the present inventors developed a cellulosebased substrate encapsulated with a polymeric film that is recyclableand lighter in weight than previous wax-saturated containers and doesnot suffer from inconsistent bonding, sealing, and conformance of a filmto the substrate. The encapsulated container is generally set forth inco-pending U.S. patent application Ser. No. 10/879,846, filed on Jun.29, 2004, from which priority is claimed in the present application.

Upon further research, the inventors discovered an additional problemrelated to cellulose based substrate encapsulation. While encapsulatedcellulose based containers have improved moisture resistance, theirmoisture-resistant characteristics are compromised if the encapsulatingfilm is not sealed correctly during manufacture or is subsequentlypunctured during manufacture or use. Hence, a problem associated withencapsulated, corrugated, cellulose based containers is that if theencapsulating polymeric film allows moisture to enter the encapsulation,the moisture wicks throughout the container and renders the containerweakened or, worse yet, inoperable.

Therefore, there exists a need for a moisture-resistant encapsulatedcontainer having improved moisture wicking resistance.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features ofthe claimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

In accordance with one embodiment of the present disclosure, a cellulosebased substrate is provided. The cellulose based substrate includes acellulose based sheet having a corrugated medium spanning between firstand second linerboards, wherein the corrugated medium includes at leastone sizing agent for moisture wicking resistance. The cellulose basedsubstrate further includes a polymeric film encapsulating at least aportion of the cellulose based sheet.

In accordance with another embodiment of the present disclosure, acontainer is provided. The container includes a cellulose based sheethaving a corrugated medium spanning between first and secondlinerboards, wherein the corrugated medium includes at least one sizingagent for moisture wicking resistance. The container further includes apolymeric film encapsulating at least a portion of the cellulose basedsheet.

In accordance with yet another embodiment of the present disclosure, acontainer is provided. The container includes a cellulose based sheethaving a corrugated medium spanning between first and secondlinerboards, wherein the corrugated medium includes a sizing agent formoisture wicking resistance and a reactive cationic cross-linking typeresin for improved wet strength. The container further includes apolymeric film encapsulating at least a portion of the cellulose basedsheet.

DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one photograph executedin color. Copies of this patent or patent application publication withcolor photographs will be provided by the Office upon request andpayment of the necessary fee.

The foregoing aspects and many of the attendant advantages of thisdisclosure will become more readily appreciated by reference to thefollowing detailed description, when taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a perspective view of one surface of a container blankencapsulated with a polymeric film in accordance with the presentinvention;

FIG. 2 is a perspective view of a container formed from the containerblank of FIG. 1;

FIG. 3 is a section taken through line 3-3 of FIG. 1;

FIG. 4 is a perspective view of one surface of a second embodiment of acontainer blank encapsulated with polymeric films in accordance with thepresent invention;

FIG. 5 is a perspective view of a container formed from the containerblank of FIG. 4;

FIG. 6 is a diagrammatic view of a process for producing a containerblank encapsulated with polymeric films in accordance with the presentinvention;

FIG. 7 is a diagrammatic view of a second embodiment of a process forproducing a container blank encapsulated with polymeric films inaccordance with the present invention;

FIG. 8 is a perspective view photograph showing a wicking testingapparatus, as described in Example 1;

FIGS. 9-12 are perspective view photographs showing wicking testingresults, as described in Example 1;

FIGS. 13 and 14 are perspective view photographs showing a wickingtesting apparatus, as described in Example 2;

FIG. 15 is a perspective view photograph showing a wicking testingapparatus, as described in Example 3;

FIGS. 16-18 are perspective view photographs showing wicking testingresults, as described in Example 3; and

FIGS. 19-24 are perspective view photographs showing wicking testingresults, as described in Example 4.

DETAILED DESCRIPTION

As used herein, the following terms have the following meanings.

Fibreboard refers to fabricated paperboard used in containermanufacture, including corrugated fibreboard.

Container refers to a box, receptacle or carton that is used in packing,storing, and shipping goods.

Moisture-resistant film refers to polymeric films that are substantiallyimpervious to moisture. Such films are not necessarily totallyimpervious to moisture, although this is preferred, but the amount ofmoisture capable of passing through the film should not be so great thatsuch moisture reduces the strength or other properties of the cellulosebased substrate to below acceptable levels.

Thermobondable refers to a property of a material that allows thematerial to be bonded to a surface by heating the material.

Thermoplastic refers to a material, usually polymeric in nature, thatsoftens when heated and returns to its original condition when cooled.

Panel refers to a face or side of a container.

Score refers to an impression or crease in a cellulose based substrateto locate and facilitate folding.

Flaps refer to closing members of a container.

Peeling refers to separation of one film from another film along a bondformed between the films.

Creep refers to movement of the film-to-film bond line that occurs whenthe films peel from each other when the bond is subjected to stress.

The present invention provides for the encapsulation of a cellulosebased substrate with polymeric films. Cellulose based substrates areformed from cellulose materials, such as wood pulp, straw, cotton,bagasse, and the like. Cellulose based substrates useful in the presentinvention come in many forms, such as fibreboard, containerboard,corrugated containerboard, and paperboard. The cellulose basedsubstrates can be formed into structures such as container blanks, tiesheets, slip sheets, and inner packings for containers. Examples ofinner packings include shells, tubes, partitions, U-boards, H-dividers,and corner boards.

The following discussion proceeds with reference to an exemplarycellulose based substrate in the form of a containerboard blank, but itshould be understood that the present invention is not limited tocontainerboard blanks.

Referring to FIG. 1, a non-limiting example of a cellulose basedsubstrate includes a container blank 20 having rectangular panels 21 and22 that will form sidewalls of a container when the blank is folded andsecured. Panels 21 and 22 are separated by rectangular panel 24 thatwill form an end wall of a container when the blank is folded. Extendingfrom the edge of panel 22 opposite the edge connected to panel 24 is anadditional rectangular panel 26 that will form a second end wall. Thesequence of panels 21, 22, 24, and 26 define a lengthwise dimension forcontainer blank 20. Each panel 21, 22, 24, and 26 includes tworectangular flaps 28 extending from the left edge and right edgethereof. Extending rearwardly from the rear edge of panel 26 is a narrowrectangular flap 30. Panels 21, 22, 24, and 26 and flaps 28 and 30 areseparated from each other by either slots 32 defined as cuts formed incontainer blank 20 or scores 34. The external peripheral edge aroundcontainer blank 20 defines a container blank periphery 36. Asillustrated, container blank 20 has a first surface defined in FIG. 1 asthe upper visible surface and a second opposite surface forming theunderside of the container blank in FIG. 1. Panel 21 and panel 22include cutouts 42 that serve as ventilation orifices, drainageorifices, or handles once container blank 20 is formed into a containerby applying adhesive to panel 30 and positioning panel 30 adjacent topanel 21. While container blank 20 is illustrated with scores, cutoutsand slots, it is understood that such features are not required and thata cellulose based substrate without such features may be encapsulatedwith polymeric films in accordance with the present invention. In theillustrated embodiment, the edge of the blank adjacent the containerblank periphery and the blank edges that define the slots and cutoutsare examples of exposed edges adjacent to which the polymeric films arebonded to each other by an adhesive, as described below in more detail.

Overlying and underlying container blank 20 are polymeric films 43adhered to the container blank and bonded and sealed to each otheraround the container blank periphery 36 by an adhesive. Polymeric films43 are also bonded and sealed to each other by an adhesive adjacent theexposed blank edges that define slots 32 and cutouts 42. As used herein,the term “sealed” means that overlapping portions of the film adjacentthe top surface and the film adjacent the bottom surface are bonded toeach other by an adhesive in a manner that substantially preventsmoisture from passing through the seal. Areas 31, identified with thestippling, correspond to locations on container blank 20 whereadditional adhesive can be applied in order to further strengthen andreinforce films 43, as described below in more detail.

Container blank 20 can be folded and secured into a container asillustrated in FIG. 2. The numbering convention of FIG. 1 is carriedforward in FIG. 2. Prior to folding container blank 20 and securing itto form a container, the portions of polymeric films 43 within slots 32are cut. Additionally prior to folding the container, the excesspolymeric film adjacent to the periphery 36 can be trimmed. Furthermore,the polymeric film spanning cutouts 42 can be cut in such a manner thata passageway is made into the interior of the container while at thesame time preserving the film-to-film seal.

Referring to FIG. 3, container blank 20 is comprised of upper linerboard 44 and lower liner board 46 spaced apart by flutes 48. An outersurface of liner board 44 is overlaid with an adhesive layer 45 andpolymeric film 43. In the illustrated embodiment, an outer surface oflower liner board 46 is overlaid with an adhesive layer 45 and apolymeric film 43. While the present invention is described in thecontext of an embodiment wherein an adhesive is applied to bothpolymeric films 43, it should be understood that satisfactory resultscan be achieved by applying adhesive only to one of the films. Theapplied adhesive 45 and polymeric films 43 conform to the topographicalfeatures defined by the peripheral edge 36, scores 34 and cutouts 42.The adhesive and films conform to the topographical features byfollowing the elevational changes in the first and second surfaces ofthe container blank. Preferably, adhesive 45 and films 43 conform to theshape and encapsulate the exposed edges of the container blank such asthose defining slots and cutouts, and seal closely against such edges asdepicted in FIG. 3. Likewise, polymeric films 43 adjacent the containerblank periphery 36 are bonded to each other at 37 by adhesive 45 toprovide a moisture-resistant seal. A similar moisture-resistant seal 39is provided between the polymeric films 43 within cutout 42.

Containerboard is one example of a cellulose based substrate useful inthe present invention. Particular examples of containerboard includesingle face corrugated fibreboard, single-wall corrugated fibreboard,double-wall corrugated fibreboard, triple-wall corrugated fibreboard andcorrugated fibreboard with more walls. The foregoing are examples ofcellulose based substrates and forms the cellulose based substrates maytake that are useful in accordance with the methods of the presentinvention; however, the present invention is not limited to theforegoing forms of cellulose based substrates.

Portions of the cellulose based substrate can be crushed before applyingthe polymeric films. Crushing of the cellulose based substrate adjacentits peripheral edges, and the edges within cutouts and slots, has beenobserved to result in improved conformance of the film to the shape ofthe edges. Crushing of the edges can be achieved by passing the edgesthrough a nip to temporarily reduce the caliper of the substrate andreduce its resilience to deformation. Crushing of the edges is commonlyachieved by placing stiff rubber rollers adjacent to cutting knives.

Polymeric films useful in accordance with the present invention includethermobondable and thermoplastic films that are moisture-resistant. Thefilms should cooperate with the adhesives, described below in moredetail, to bond the films together and provide moisture-resistant sealsbetween the overlapping portions of the films. The adhesive mayadditionally bond the films to the cellulose based substrate. Usefulfilms may be a single-layer or may be a multi-layer, e.g., a two or morelayer film. Single-layer films are preferred. The choice of a specificfilm composition and structure will depend upon the ultimate needs ofthe particular application for the cellulose based substrate. Filmsshould be chosen so that they provide the proper balance betweenproperties such as flexibility, moisture resistance, abrasionresistance, tear resistance, slip resistance, color, printability, andtoughness.

In certain embodiments, co-extruded multi-layer polymeric films can beused. Multi-layer films provide the ability to choose an inner layercomposition that cooperates with the adhesive while at the same timeproviding an outer layer that has properties more appropriate for theexposed surfaces of the encapsulated container.

Exemplary films include linear low density polyethylene (LLDPE) blendedwith low density polyethylene (LDPE), blends of LLDPE and ethylene vinylacetate (EVA) copolymer, blends of LLDPE and ethylene acrylic acid(EAA), coextruded films comprising LLDPE and EVA layers, coextrudedfilms of an LLDPE-LDPE blend and EVA, coextruded films having an LLDPElayer and an EAA or ethylene methacrylic acid (EMA) layer, or coextrudedfilms having an LLDPE-LDPE layer and an EAA or EMA layer. Examples ofother useful film layers include those made from metallocene, Surlyn®thermoplastic resins from DuPont Company, polypropylene,polyvinylchloride, or polyesters or combination thereof in a monolayeror multi-layer arrangement.

Film thickness can vary over a wide range. The film should not be sothick that when it is applied to a container blank it will not conformto changes in topography along the surface of the container blankcreated by such things as the peripheral edges, edges defined by theslots, and edges defined by the cutouts. The films should be thickenough to survive normal use conditions without losing theirmoisture-resistance. Exemplary film thicknesses range from about 0.7 mil(0.018 mm) to about 4.0 mil (0.10 mm).

The moisture-resistant polymeric film applied to the inner and outersurfaces of the container blank can be the same, or different films canbe applied to different surfaces. Choosing different films for therespective surfaces would be desirable when the particular propertiesneeded for the respective surfaces of the container blank differ.Examples of film properties that might be chosen to be different on therespective surfaces of the container blank have been described above. Inaddition to being colored, it is possible that graphics may bepreprinted on the polymeric film. For food applications, the film ispreferably approved for use by the United States Food and DrugAdministration.

Adhesives useful in accordance with the present invention include thosethat cooperate with the films to bond the films together and optionallyto the underlying cellulose based substrate. The adhesive and filmcombination should be such that the two are able to conform to theexposed edges of the container blank. Preferably, once the adhesive andfilm are conformed to the edges of the container blank and the adhesivehas set, any peeling of the films and creep adjacent such edges isminimal. The adhesive and films should be chosen so that the bondbetween the films formed by the adhesive has a cohesive strength that isgreater than the stresses that the bonds are exposed to duringmanufacturing and use of the encapsulated container. For example, thefilm and adhesive should be chosen so that the bond between the filmsformed by the adhesive has a cohesive strength that is greater than thestresses that promote peeling of the films adjacent the container blankedges. By choosing the films and adhesives so that the bond between thefilms formed by the adhesive has a cohesive strength greater than thestresses promoting peeling, creep of the peeling can be minimized.Preferably, the adhesive will remain with the polymeric films when theencapsulated container blank is re-pulped, e.g., during recycling.Exemplary types of adhesives are known as hot melt adhesives, andinclude elastic styrene-isopropene-styrene block copolymers. Otheruseful adhesives include ethylene vinyl acetate adhesives, amorphouspolyolefin adhesives, polypropylene adhesives, and pressure sensitiveadhesives. Preferably, the adhesives have a viscosity ranging from about1,000 to 15,000 centipoise at the application temperature. While hotmelt adhesives are preferred, it should be understood that non-hot meltadhesives may find utility in the present invention and that othercompositions of adhesives may also be used.

Referring to FIG. 4, in another embodiment of the present invention acontainer blank 50 includes panels 21, 22, 24, and 26 that arestructurally separated from each other as well as from flaps 28 and flap30. In this embodiment, polymeric resistant films 43 function as a hingebetween the respective panels of the container blank. As with FIG. 1,container blank 50 in FIG. 4 is illustrated with stippled areas 31 thatidentify locations where additional adhesive may be added to reinforcefilms 43.

Container blank 50 can be folded and secured into a container asillustrated in FIG. 5. The numbering convention of FIG. 4 is carriedforward in FIG. 5.

Referring to FIG. 6, a method for producing a cellulose based substrateencapsulated in a polymeric film on a continuous basis, as opposed to abatch basis is illustrated and described in the context of acontainerboard blank. In the illustrated embodiment, a container blank20 from a source of container blanks (not shown) is delivered via aconveyance system illustrated as two sets of rollers 52 to a filmapplication stage 53. At film application station 53, films 56 and 58are unrolled from the supply rolls and delivered to a nip formed byrollers 54. Before entering the nip at rollers 54, adhesive is appliedto the surface of the respective films that will contact the uppersurface 38 and lower surface 40 of container blank 20. In thisembodiment, adhesive is applied to both films 56 and 58; however, asnoted above, adhesive can be applied to only one of films 56 or 58. Thefollowing description applies equally well to an embodiment whereinadhesive is applied to only one of the films 56 or 58.

In the embodiment of FIG. 6, adhesive is applied to substantially all ofthe surface of films 56 and 58, particularly those portions where directfilm-to-film bonding is necessary, e.g., around the container blankperiphery and adjacent the edges defined within cutouts and slots. Itshould be understood that it is not required that adhesive be applied tosubstantially all of the surfaces of films 56 and 58. Satisfactoryfilm-to-film bonding can be achieved by applying adhesive only to thoseportions of the films that overlap around the container blank peripheryand adjacent the edges defined within cutouts and slots. Adhesive ispreferably provided by a non-contact application method in order tominimize burn-through or tearing of films 56 and 58. An exemplaryapplication process includes applying a hot melt adhesive as carefullycontrolled extruded fibers filaments of the adhesive applied in acrossing pattern. Equipment suitable for applying adhesives in thismanner is available from Nordson Corporation of Dawsonville, Ga.Adhesive can be applied in other manners such as slot die methodswherein the film contacts a die as the adhesive is dispensed or spraytype application methods.

The location where the adhesive is applied can vary; however, when theadhesive is heated, it is preferable to add the adhesive as close to thenip formed by rollers 54 as possible in order to avoid premature coolingof the adhesive. In order to facilitate wetting of the film surfaces bythe adhesive, the film surfaces can be treated such as by coronatreatment (not shown). The adhesive should be applied at temperaturesthat do not adversely affect the moisture-resistant properties of thefilm and do not damage the film or the underlying container blank. Theapplication rate for the adhesive can vary. Exemplary application ratesinclude about 1 gram per square meter to 15 grams per square meter. Whennecessary, more adhesive can be applied to those areas where added bondstrength is desirable such as areas prone to tears or where addedthickness can reduce abrasion damage. After the adhesive is applied,film 56 is provided adjacent upper first surface 38 of container blank20, and film 58 is provided adjacent lower second surface 40 ofcontainer blank 20. Films 56 and 58 have a width dimension measured inthe cross-machine direction that is greater than the width of containerblank 20. Thus, portions of the films 56 and 58 extend beyond the edgesof the blanks that are parallel to the direction that the blanks travel.In the direction that the blanks travel through the process, individualblanks are spaced apart. Accordingly, films 56 and 58 bridge the spacebetween the trailing edge of one blank and the leading edge of the nextblank.

The combination of container blank 20, first film 56 and second film 58passes through the nip formed by rollers 54. The nip formed by rollers54 defines an inlet to a pressure chamber 60. Pressure chamber 60 is influid communication with a pump 62 capable of increasing the pressurewithin pressure chamber 60. Pressure chamber 60 also includes aplurality of rollers 64 for supporting the combined container blank 20,first film 56 and second film 58 through pressure chamber 60. Pressurechamber 60 is operated at a pressure greater than the pressure outsidepressure chamber 60. As described below in more detail, the elevatedpressure within pressure chamber 60 promotes the conformance of films 56and 58 to container blank 20 around the container blank peripheral edgesas well as within any slots or cutouts provided in the container blank.The container blank 20 and films 56 and 58 exit chamber 60 through thenip created by rollers 66. The nips created by rollers 54 and 66 arepreferably as airtight as possible in order to maintain the elevatedpressure within chamber 60. Alternative means can be used besides therollers to prevent pressure loss from chamber 60, such as air locks andthe like. From pressure chamber 60, container blanks 20 encapsulated byfilms 56 and 58 pass to trimming stage 78 described below in moredetail.

As noted above, films 56 and 58 are dimensioned such that the respectivefilms extend beyond the container blank periphery in the cross machinedirection perpendicular to the travel of the container blank 20. In thismanner, film 56 comes into contact with film 58 adjacent the containerblank periphery and within slots and cutouts where the films overlap.The presence of adhesive between these overlapping portions of the filmcauses the films to be held together. As the adhesive cools, thecohesive strength of the bond formed by the adhesive between the filmsincreases. Preferably, the adhesive bonds the films to each other atsubstantially all points where the films overlap. In this manner, thefilms form an envelope that substantially encapsulates the containerblank. As described below in more detail, the envelope is formed in amanner such that a pressure differential may be provided between theenvironment inside the envelope and the environment outside theenvelope. An envelope formed around the container blank is suitable solong as it encapsulates the blank in a manner that is capable ofsupporting a pressure differential between the inside of the envelopeand the outside. For example, two films bonded to each other adjacentthe leading and trailing edges of a container blank, but not theparallel side edges, would not substantially encapsulate a blank so asto be able to support a pressure differential between an environmentbetween the films and an environment outside the films; however, anenvelope formed by the films wherein the films are intermittently orreversibly bonded around all exposed edges of the container blank wouldbe satisfactory, because a pressure differential can be created betweenthe interior of the envelope and the environment exterior to theenvelope.

Conformance of the two films to the container blank periphery, slots,and cutouts, is promoted by providing a pressure differential between anenvironment within the envelope described above and the environmentexterior of such envelope. More specifically, the container blank andfilms are treated so that there is a point in the manufacturing processafter the adhesive has been applied to at least one of the films wherethe pressure within the envelope is lower than the pressure exterior tothe envelope. Satisfactory conformance of the films is evidenced by anabsence of air bubbles at the interface between the films and thecontainer blank, as well as robust and continuous seals around theexposed edges of the container and the edges exposed within the cutoutsand slots. The degree of the conformance of the films to the containerblank can be evaluated by assessing the distance between thefilm-to-film bond line and the exposed edge of the container blank. Asthe distance between the film-to-film bond line and the container blankedge increases, the degree of conformance of the film to the containerblank edge decreases. Shorter distances between the container blank edgeand the film-to-film bond line are more desirable than larger distances.

As used herein, the phrase “pressure differential” refers to adifference in pressure between the inside of the envelope and theexterior of the envelope that is attributable to more than the pressuredifferential that would be observed by simply reducing the temperatureof gas within the envelope without a phase change. For example, in thecontext of the present invention, a pressure differential can beprovided by moving the envelope from a low pressure environment to ahigher pressure environment, with or without cooling of the gas withinthe envelope.

Pressure within pressure chamber 60 can vary and should be chosen sothat crushing of the container blank is avoided while at the same time,conformance of the film to the blanks is high. The pressure in chamber60 should not be so high that excessive gas loss cannot be prevented byrollers 54 and 66. Rollers 54 and 66 should be operated at a pressurethat is high enough to minimize gas loss while at the same time notbeing so high that unwanted crushing of the container blank occurs.Examples of suitable rollers include silicone rubber rollers that areeither patterned or non-patterned. The particular pressure within thechamber will depend upon a number of factors, including the thicknessand malleability of the film. Thinner more malleable films will conformto the container blank with less pressure than thicker, stiffer films.The chamber should be long enough so that the adhesive is able to gainadequate cohesive strength through cooling as it passes through pressurechamber 60. As discussed above, an adequate cohesive strength is onethat is greater than the tension force that promotes peeling of thefilms from each other. The length of pressure chamber will also dependupon the speed of the blanks passing through the chamber. Exemplarypressures within the pressure chamber can range from about 2 to 20pounds per square inch. Blank speeds ranging from about 1 to 500 feet(0.3 to 150 meters) per minute are exemplary.

Within trimming stage 78, sensor 80 and laser 82 cooperate to trim awayexcess polymeric film around the container blank periphery and withinthe slots and cutouts without compromising the water-resistant seals. Inorder to ensure the accuracy of the film trimming, trimming stage 78preferably employs a conveyance system 83, such as a vacuum belt thatminimizes movement of the container blank and films during the lasertrimming process. Alternatives to laser trimming include die cutting orhand trimming.

By trimming away portions of the polymeric films within the cutouts,openings can be provided for ventilation, drainage, or for allowing thecutouts to serve as handles for the container. It is preferred thattrimming of the films within the cutouts and slots be carried out assoon as possible after the adhesive forms the film-to-film bonds.Peeling of the films occurs when the tension on the films is greaterthan the cohesive strength of the film-adhesive-film bond. When thefilms conform to the contour of the edges of the container blank, thefilms are put under tension that can cause peeling. Peeling is evidencedby the films separating along the line where the upper film meets thelower film. As the films begin to peel, this line begins to creep awayfrom the edge of the container blank. As peeling may increase over time,it is preferable to minimize the time between when the encapsulatedblank leaves the pressure chamber and the time when the trimming occurs.The films adjacent the exposed edges should be trimmed as close aspossible to the container blank edges without compromising thefilm-to-film bond at the time of trimming. The distance between the edgeof the container blank and the edge of the trimmed film should be greatenough that any peeling of the films does not extend to the trimmed edgeof the films and compromise the seal between the films.

Referring to FIG. 7, a cellulose based substrate encapsulated bypolymeric films can be produced by a method wherein pressure chamber 60of FIG. 6 has been replaced by a vacuum chamber 84. The systemillustrated in FIG. 7 includes trimming stage 78 identical to thetrimming stage described above with respect to FIG. 6. The system ofFIG. 7 also includes a film application stage 86 that is identical tothe film application stage 53 in FIG. 6 with the exception that adhesiveapplicators 59 are omitted.

Vacuum chamber 84 is an air tight chamber in fluid communication withvacuum pump 88. The inlet of vacuum chamber 84 includes rollers 94defining a nip designed to allow a container blank 20 and associatedfilms 56 and 58 to pass into chamber 84 without compromising the reducedpressure therein. Upstream from rollers 94 are a pair of rollers 92 thatreceive films 56 and 58 and container blank 20. Films 56 and 58 arepositioned adjacent to the upper and lower surface of blank 20 atrollers 92. When container blank 20 includes corrugated fibreboard andthe flutes are oriented parallel to the direction of travel of theblanks, when the leading edge of the container enters vacuum chamber 84,a suction is created at the trailing end of the container blank. Thissuction draws films 56 and 58 against the trailing end of containerblank 20 and serves to create a seal that prevents air from being drawninto vacuum chamber 84 through the corrugated flutes of container 20.

Vacuum chamber 84 includes a conveyor belt 96 for transporting blanks 20through vacuum chamber 84. Vacuum chamber 84 also includes a combinationof rollers 98, 100 and 102 for separating films 56 and 58 from containerblank 20 and delivering the films to an adhesive applicator 104 whereadhesive is applied to a surface of the films 56 and 58 before they arerecombined with blanks 20. As noted above, in the illustratedembodiment, adhesive is shown as being applied to surfaces of both films56 and 58; however, this embodiment is not limited to applying adhesiveto both films and accordingly, adhesive can be applied to either film 56or 58. The exit of vacuum chamber 84 includes a pair of rollers 106defining an air tight nip at the exit of chamber 84.

In accordance with this process employing a vacuum chamber, containerblanks 20 are combined with films 56 and 58 at film application stage86. The web comprising the container blank 20 and films 56 and 58 entervacuum chamber 84 at the nip formed by rollers 94. As films 56 and 58enter vacuum chamber 84, they are separated from container blank 20 anddelivered to adhesive applicators 104 where adhesive is applied to thesurface of at least one of the films. As soon as possible after adhesiveapplicators 104, films 56 and 58 are recombined with container blanks20. The amount of time between when adhesive is applied to the films andwhen the films are applied to the container blank should be minimized inorder to avoid the adhesive losing its adhesive properties due tocooling.

The combination of films 56 and 58 and the adhesive form an envelopeencapsulating container blank 20. Pressure within this envelope will beapproximately equal to the pressure within vacuum chamber 84.Accordingly, as the envelope exits vacuum chamber 84, it will be exposedto the environment outside vacuum chamber 84 which preferably isatmospheric pressure. The pressure differential between the internalenvironment within the envelope and the environment outside the envelopepromotes the conformance of the film to the container blank, includingthe exposed edges around the container blank periphery and edges definedwithin cutouts and slots. After the adhesive cools, the web of films,adhesive, and container blank is delivered to trimming stage 78 wherethe encapsulated blank is processed as described above.

In the process illustrated in FIG. 7, it is preferred that the films asthey exit the vacuum chamber adhere to each other at substantially allpoints where they overlap so that the films form an envelope thatsubstantially encapsulates the container blank. While it is preferredthat the films are reversibly or intermittently bonded to each otheradjacent all four edges of the container blank and within any slots andcutouts of the container blank, as discussed above, an envelope formedaround the container blank is suitable so long as it is capable ofsupporting a pressure differential between the inside of the envelopeand the outside.

Exemplary vacuum conditions within vacuum chamber 84 can range fromabout 200 mm Hg to about 300 mm Hg. Vacuum within vacuum chamber 84should be chosen so that it is far enough below the pressure outsidevacuum chamber 84 so that acceptable conformance of films 56 and 58 tocontainer blank 20 is achieved after the encapsulated blank exits thevacuum chamber. Vacuum within vacuum chamber 84 should not be so lowthat film damage occurs, the container blank experiences loss of caliperor the vacuum cannot be maintained by the seals at the inlet and outletof the vacuum chamber. The description regarding the types of films,adhesives, film properties, adhesive properties, adhesive loading, linespeeds and the like described above with respect to FIG. 6 are alsoapplicable to the process of FIG. 7.

Although not illustrated, other methods of promoting the conformance ofthe polymeric films to the container blank can be used. One example ofsuch method includes a hot air knife capable of delivering a focusedstream of air at the encapsulated container blank as it leaves thepressure chamber 60 of FIG. 6 or the vacuum chamber 84 of FIG. 7.

With the reference to FIGS. 6 and 7, the inlets and outlets of therespective vacuum chamber 60 and pressure chamber 84 are described asincluding rollers. It should be understood that combinations of othertypes of components such as brushes, soft rollers, and wiper blades thatallow for the entry and exit of the container blanks and films into thevacuum chamber or pressure chamber without substantially compromisingthe reduced or increased pressure within the respective chambers can beutilized. For example, one alternative includes a combination of a softroller and a flexible wiper for sealing the upper surface of thecombination of a container blank and film to the vacuum/pressure chamberand a brush for sealing the lower surface of the blank and film to thevacuum/pressure chamber.

The present invention has been described above in the context of acontainerboard blank encapsulated with a polymeric film. Thecontainerboard blank can be formed and secured to provide amoisture-resistant container. In addition, such a moisture-resistantcontainer can be combined with other structural components such as innerpackings, described above, that may be encapsulated with a polymericfilm, or may not be encapsulated with a polymeric film. Furthermore,containers can be provided wherein the container body is notencapsulated with a polymeric film while certain inner packingstructural components are encapsulated with a polymeric film. Inaddition, cellulose based inner packings encapsulated with a polymericfilm can be combined with non-cellulosic based container bodies andcellulose based container bodies encapsulated with polymeric film can becombined with non-cellulosic inner packing structural components.

The moisture wicking resistance properties of the flutes or corrugatedmedium 48 in accordance with the present disclosure will now bedescribed in greater detail. Embodiments of the present disclosureachieve moisture wicking resistance in the container 20 whilemaintaining adhesive properties between the corrugated medium 48 and thelinerboards 44 and 46. In that regard, the corrugated medium 48 istreated with at least one additive designed to enhance the sizing of thecorrugated medium 48.

As described above, the container or container blank 20 is suitablyformed from a cellulose based sheet having flutes or corrugated medium48 spanning between the first and second linerboards 44 and 46. Thecontainer or container blank 20 includes a polymeric film encapsulatingat least a portion of the cellulose based sheet. In some instances,there will be holes in the container encapsulation films, whether fromfilm manufacturer defects, the container manufacturing process, orcontainer packing and handling issues. As described in greater detail inthe Examples provided below, a container that has such a hole (or holes)and is exposed to free water will wick water, so long as there is freewater to be absorbed or until the total saturation point of thecontainer is reached, unless the corrugated sheet (including thelinerboard and the corrugated medium) has low-wicking properties.Moreover, as described in the Examples provided below, encapsulatedcontainers tend to wick water more readily that unencapsulatedcontainers.

Most corrugated cellulose based containers are formed from cellulosebased sheets having a corrugated medium spanning between the first andsecond linerboards. The corrugated medium is typically adhered to thefirst and second linerboards using a water-based adhesive. Conventionalpractice in the field of corrugated cellulose based containers is tomanufacture the first and second linerboards with a sizing agent, whichprovides some moisture-resistance in the first and second linerboards,but to manufacture the corrugated medium with little to no sizing, ascompared to the first and second linerboards.

It was believed that such manufacturing processes allow the water-basedadhesive to sufficiently penetrate the corrugated medium and provide asuitable bonding site between the corrugated medium and the linerboards.However, such manufacturing processes allow for water or moisture towick through the corrugated medium and spread to the linerboards. Afterwater has wicked throughout an encapsulated cellulose based container,the container will be damaged and will likely fail under the load of thecontents within the container.

Therefore, conventional practice in the field of corrugated cellulosebased containers has been to manufacture the corrugated medium withlittle or no sizing agents. Contrary to conventional practice, the sizedcorrugated medium, in accordance with the present disclosure, providesmoisture wicking resistance to the container while still obtaining asuitable adhesive bond. Moreover, such a bond can be improved byincreasing the roughness factor of the corrugated medium.

It should further be appreciated that water-resistant adhesives are alsowithin the scope of the present disclosure. Water resistant adhesivesobtain a suitable bond between the corrugated medium and linerboardswhile further improving the moisture resistance of the corrugatedcellulose based containers described herein.

In one embodiment, the corrugated medium 48 includes alum, which is anadditive designed to size the natural resins to form hydrophobic groupswithin the cellulosic fiber. Alum is generally added to virgin cellulosefiber, as opposed to recycled fiber. Regarding recycled fiber, thenatural resins in the fiber tend to break down in the drying and/orrepulping process. For this reason, alternative agents are added tosecondary or recycled fiber.

In another embodiment, the corrugated medium 48 includes a sizing agent.As a nonlimiting example, the sizing agent is a reactive sizing agent,such as alkyl ketene dimer (AKD), alkenyl ketene dimer emulsion (ALKD),alkenyl succinic anhydride (ASA), or any blends of the foregoingadditives, such as ASA/ALKD blends. It should be appreciated, however,that non-reactive sizing agents (such as rosin and paraffin waxemulsions) and other surface treatments (such as styrene maleicanhydride (SMA), styrene acrylic emulsion (SAE), polyacrylamides (PAE),colloidal silica, and cellulosics) are also sizing agents within thescope of the invention.

In accordance with embodiments described herein, the reactive sizingagent is present in the corrugated medium in an amount in the range ofabout 0.1 to about 10.0 lbs/ton. In another embodiment, the reactivesizing agent is present in the corrugated medium in an amount in therange of about 0.1 to about 4.0 lbs/ton. Variations in the amount ofreactive sizing agent are generally a result of variations in amount ofvirgin fiber versus secondary or recycled fiber used in the product, aswell as the papermaking conditions.

Linerboards of a corrugated substrate generally have moisture wickingresistance properties similar to the corrugated medium described herein,whether sized by alum or the sizing agents described herein.

It should be apparent that the principles of including a sizing agentfor moisture wicking resistance in the corrugated medium describedherein are not limited to container encapsulation methods by adhesivebonding, but also extend to other encapsulation methods. It shouldfurther be appreciated that the principles of including a sizing agentfor moisture wicking resistance in the corrugated medium are not limitedto encapsulated containers, but also extend to unencapsulatedcontainers.

In another embodiment, the cellulosic pulp is treated with both a sizingtreatment, as discussed above, and a wet strength resin, such ascationic polyamide-epichlorohydrin reaction products (PAE resins).Methods of enhancing the strength of cellulosic products with PAE resinsis described in U.S. Pat. No. 5,830,320, the disclosure of which ishereby expressly incorporated by reference. As described in U.S. Pat.No. 5,830,320, a cellulosic fiber product comprises about 5-40% of thecellulosic fiber treated with 0.5-5.0% of a reactive crosslinking-typewet strength resin additive substantially uniformly blended with 95-60%of untreated fiber.

The PAE resin is at least partially crosslinked and may be selected fromthe following: urea-formaldehyde condensation products,melamine-urea-formaldehyde condensation products, andpolyamide-epichlorohydrin reaction products.

In addition to improving wet strength, such treatment with PAE resinincreases the dry strength of the cellulosic fiber product and improvesthe repulpability of the fibers when recycled. Therefore, in anotherembodiment, 10-30% of the cellulosic fiber is treated with 0.5-5.0% of areactive crosslinking-type wet strength resin additive. In anotherembodiment, the cellulosic fiber product contains from about 0.1-0.6% byweight of the resin based on the total amount of cellulosic fiber in theproduct.

Advantages of moisture wicking resistance properties in the corrugatedmedium in accordance with the present disclosure include increasedcontainer integrity and strength when exposed to water and/or watermigration. For example, in produce-packing applications, water or ice isadded to produce to keep the produce fresh during transportation. If theencapsulation structure is damaged and allows moisture to enter theencapsulation, the embodiments disclosed herein prevent water fromwicking throughout the encapsulated cellulose based substrate or sheet.Therefore, the wicking resistance properties of the container describedherein provide for wicking prevention and maintain container integrityeven if water enters the encapsulation structure.

Examples 1-6 that follow illustrate the improved strength of containersconstructed in accordance with embodiments of the present disclosure ascompared to previously developed (or “control”) containers.Specifically, the Examples indicate that water tends to wicksignificantly less in Low Wicking Medium container board, as compared toControl container board. Moreover, wicking in the Low Wicking Medium wasobserved to be more prevalent in encapsulated samples than inunencapsulated samples, indicating that encapsulation encourageswicking. In addition, the Examples indicate that the moisture wickingdirectly impacts the top-to-bottom strength of the container and thatthe Low Wicking Medium containers have superior strength performanceover the Control Medium containers. In that regard, the Low WickingMedium encapsulated containers only lost 25% of their top-to-bottomstrength when exposed to a water mist shower for seven days. The ControlMedium encapsulated containers, on the other hand, lost 73% of theirtop-to-bottom strength.

EXAMPLE 1 Wicking Testing for Unencapsulated Cellulose Based Sheets

The basis for the wicking testing provided in this example is inaccordance with the Springfield Wick Test W-30. Several modificationswere made to accommodate the use of combined corrugated container boardrather than the individual paper samples that the test is designed for.The first modification was to cut the samples to a size of 11 inches×2inches to be large enough for the encapsulation process (described belowin Example 3). As seen in FIG. 8, the samples were cut such that theflutes of the corrugated medium were oriented in the vertical directionto allow for maximum wicking directly up the flutes. The secondmodification was to measure only on the sides of the samples for wickingbecause the sample sides were the only points for measurement withoutopening up the linerboards of the samples to expose the corrugatedmedium and thereby destroy the sample. The third modification wasregarding time for testing: one set of unencapsulated samples was leftfor 3 hours and a second set was left for 72 hours.

The “Control Medium” samples were cut from a C-flute corrugatedcontainer board, having standard low-wicking linerboards and a standardmedium (i.e., without a sizing agent). The “Low-Wicking Medium” sampleswere also cut from a C-flute corrugated container board from the samemanufacturer under the same manufacturing conditions, but havingstandard low-wicking linerboards and a low-wicking medium (i.e., with asizing agent).

As seen in FIG. 8, four test samples were set up in the testingapparatus. The two samples on the left are Control Medium samples andthe two samples on the right are Low-Wicking Medium samples. Per testprotocol, 450 ml of deionized water was added to the pool at the bottomof the testing apparatus. Accordingly, approximately 1.3 cm of eachsample was submerged in the water pool at all times.

During testing, it was observed that the Control Medium samples began towick water immediately on contact with the water pool. The Low-WickingMedium samples had no immediate wicking. In all cases, the linerboardsof the samples wicked very little water compared to the corrugatedmedium. Most of the wicking was completed within less than 2 hours oftesting. Water did continue to wick after that initial period, but at asignificantly reduced rate.

The Control Medium samples wicked water a distance of approximately 5.8cm above the level of the water pool, while the Low-Wicking Mediumsamples wicked approximately 1-2 mm above the level of the water pool.As seen in FIG. 9, the linerboard of the Low-Wicking Medium sampleswicked water only slightly above the surface of the pool, approximately1-2 mm.

As seen in FIG. 10, the Control Medium sample is situated on the leftand the Low-Wicking Medium sample is situated on the right. At firstglance, it appears that both sets of samples completed the test withsimilar results. However, upon closer examination (see FIG. 11), theControl Medium sample wicked significantly more water (4.5 cm above poolsurface) than the Low-Wicking Medium sample (2 mm above pool surface).Referring back to FIG. 10, a thin dark line on the right side of the twoControl Medium samples indicates the wicking level of the sample wherethe soaked medium has lost it shape and emerges from the side of thesample. There is no such line on the Low-Wicking Medium samples.

The test that was run over a 72-hour period had similar results to the3-hour test. As seen in FIG. 12, there was slightly more wicking by thelinerboards over the longer time period. However, the test results weresubstantially similar to the 3-hour test results. In the 72-hour test,the water wicked up the Control Medium sample to a distance ofapproximately 5.0 cm, as compared to the 4.5 cm in the 3-hour test. TheLow-Wicking Medium samples wicked to distance of approximately 3-4 mm,as compared to 2-3 mm in the 3-hour test.

EXAMPLE 2 Compression Testing for Encapsulated Containers

Two sets of nine, 4″×4″×4″ regular slotted containers manufactured fromthe same materials used for the wicking testing in Example 1 were diecut. (Regular slotted containers in accordance with the presentdisclosure include flaps all having the same length, with the two outerflaps being one half of the container width to meet in the middle.) Thenine Control Medium containers were marked with a “C” and sent with thenine Low-Wicking Medium containers to be encapsulated. The bottom flapsand the manufacturer's joint were closed using hot melt, and two 1 mmholes were punched into consecutive bottom slots of all of thecontainers. As seen in FIGS. 13 and 14, the containers were placed in atray and filled with ice. The tray was placed in a cooler for seven daysat a temperature of approximately 35° F.

After seven days the containers were removed from the cooler and takendirectly to be top-to-bottom compression tested. The results in Table 1below show a significant difference in compression results betweencontainers made from the Control Medium container board (126.67 lbfaverage) and containers made from the Low-Wicking Medium container board(171.22 lbf average). TABLE 1 COMPRESSION TEST RESULTS Low-WickingControl Medium Medium Peak Force Avg. (lbf) 126.67 171.22 Std. Deviation61.0287 20.0984 Peak Displacement Avg. 0.1918 0.2951 Std. Deviation0.0932 0.2025

The largest contributing factor to the Control Medium sample containershaving low average results was that two of the Control Medium samplecontainers were completely saturated with water inside theencapsulation. In that regard, the containers had wicked water into thewhole structure of the container. These two saturated containers hadpeak force readings of 23 lbf and 28 lbf. However, even with those twocontainers disregarded from the average test results, the remainingControl Medium sample containers averaged 155.57 lbf, stillsignificantly less than the compression strength of the Low-WickingMedium sample containers at 171.22 lbf. These results suggest that thecontainers having a Low-Wicking Medium provide additional strength, ascompared to containers with a medium that wicks, because the Low-WickingMedium does not “pull” (or wick) free water into the structure of thecontainer.

Therefore, incorporating a medium having low-wicking properties into anencapsulated container apparently improves the ability of the finishedcontainer to continue to provide structural strength when theencapsulation is compromised and the container is exposed to free water.

EXAMPLE 3 Wicking Tests for Encapsulated Cellulose Based Sheets

An additional wick test was done using the same corrugated material asused in Example 1, except in encapsulated form (see FIG. 15). Eachsample was encapsulated by a standard encapsulating process and had two1 mm holes punched through the encapsulation film at the bottom of thesample to allow exposure to the water.

The basis for the wicking portion of the testing was again theSpringfield Wick Test W-30, with the same modifications described abovein Example 1. Again, 450 ml of deionized water was added to the pool atthe bottom of the testing apparatus.

From the same materials as the samples used in the previous examples,the encapsulated Control Medium samples were cut from an encapsulatedC-flute corrugated container board, having standard linerboards and astandard medium. The encapsulated Low-Wicking Medium sample were cutfrom an encapsulated C-flute corrugated container board, having standardlinerboards and a Low-Wicking Medium. As seen in FIG. 15, the twosamples on the left are the Control Medium samples and the two sampleson the right are the Low-Wicking Medium samples.

Unlike the unencapsulated samples in Example 1, the encapsulationmaterials in this example prevented measurements of water wicking atinterim times during the 72-hour test. FIG. 16 shows the samplesimmediately after being removed from the test after 72 hours. The twoencapsulated Control Medium samples on the left have linerboards wettedapproximately 2-3 mm above the level of the pool. However, lookingcarefully, dark staining is apparent along the flute lines on the faceof the sample. Thus, water appeared to have wicked along the corrugatedmedium, transferring into the linerboards along the adhesive linesbetween the corrugated medium and the linerboards. It does not appear,however, that water entered between the encapsulating film and thelinerboards.

The encapsulated Low-Wicking Medium samples on the right include onesample having a water mark approximately 1-2 mm above the level of thewater pool and one sample having no indication of a water mark. Neithersample has any water staining along the flute lines, as observed in theControl Medium samples.

Referring to FIG. 17, the corrugated medium of the encapsulatedLow-Wicking Medium sample that wicked water is exposed. This samplewicked water at a highest point of approximately 4.2 cm above the levelof the water pool. The corrugated medium, while wet, was not entirelysaturated. In addition, the water did not permeate the sample along aneven water line across the sample. Rather, the high-water line appearedto be at the third and fourth flutes from the left. When accessing thecorrugated medium, there was some fiber tear along the left-hand edgeand the third flute line from the right below the high-water line,indicating that the adhesive bond was still in place and had notdissolved.

Referring to FIG. 18, the corrugated medium of one of the encapsulatedControl Medium samples is seen. Both of the encapsulated Control Mediumsamples wicked water approximately 21.2 cm above the level of the waterpool. Unlike the Low-Wicking Medium samples, the medium of the ControlMedium samples is completely saturated. Although not evident in FIG. 18,this sample glistened with free water. No fiber tear was present on thesample below the high water line, indicating that the adhesive bond wasdissolved.

Notably, the encapsulated Low-Wicking Medium sample that wicked waterdrew considerably more water than the unencapsulated counterpartspreviously described in Example 1 (4.2 cm versus 1-2 mm). Both sampleswere cut from the same piece of container board; therefore, theseresults indicate that the encapsulation or the process of encapsulationencourages wicking. It is believed that the encapsulated Low-WickingMedium sample that did not wick water was not adequately prepared withpuncture holes. For example, the puncture holes may have been closed offby the excess material from the encapsulating film that deformed when ittouched the bottom of the water pool.

The encapsulated Control Medium samples also wicked considerably morewater than their unencapsulated counterparts described in Example 1(21.2 cm versus 5.0 cm). Again, both samples were cut from the samepiece of board; therefore, these results further indicate that theencapsulation or the process of encapsulation has an enhancement effecton water wicking.

EXAMPLE 4 Wicking Testing for Encapsulated Containers

Two samples of encapsulated broccoli containers were obtained. A holewas punctured in the top flap locking hole. In an effort to determinehow a large quantity of penetrating water affects an encapsulatedcontainer in terms of container strength and water migration, 400 ml ofdeionized water was poured down the exposed flutes of the container.

Both sample containers had the same 69# liners from the same rolls:mottled white on the double back side and standard kraft for the singleface. The difference between the two containers was the corrugatedmedium. The first sample container is the Control Medium containerhaving a 36# FPT Medium (Spec. No. 4490). The second sample container isthe Low-Wicking Medium container having a 36# FPT Low-Wicking Medium(Spec. No. 4491).

Using a squeeze bottle, 400 ml of deionized water was injected into eachcontainer over a 10-minute period into one corner of the containeropposite the manufacturer's joint. As seen in FIGS. 19 and 20,approximately 20 minutes after the water had been introduced, theLow-Wicking Medium container (FIG. 19) has only one small spot on thebottom flap that looks wet. The Control Medium container (FIG. 20), onthe other hand, has multiple areas where the linerboard was wetted out,particularly evident along the flute lines on the bottom flap. Bothcontainers had water damage in the form of pock marks in the flutes downthe side wall below the hole locking area where the water wasintroduced.

Both containers were allowed to stand for 44 hours. Referring to FIGS.21 and 22, the bottom flap directly below the point of entry of theLow-Wicking Medium container (FIG. 21) was completely saturated andwater had moved fairly evenly up the side wall approximately 3.5 inches(denoted by the red/black line hand drawn on the container). Water hadjust passed the corner on both short side panels. Where the line goesstraight up the side wall is the area where the water was initiallyintroduced by pouring.

The Control Medium container (FIG. 22) has significantly more waterdamage than the Low-Wicking Medium container (FIG. 21). The bottom flapdirectly below the point of entry was completely saturated. Visualinspection of the Control Medium container showed that water hadcompletely saturated the linerboards. As seen in FIG. 22, the water inthe Control Medium container moved up the side walls to a depth ofapproximately 9.5 inches and had migrated around the corners to abouthalf way on both side panels.

Referring to FIGS. 23 and 24, photos taken 235 hours after the initialwetting show consistent results with the results described above. In theLow-Wicking Medium container (FIG. 23), water had not wicked any furtherinto the container structure from the initial migration (FIG. 21). Inthe Control Medium container (FIG. 24), water had continued to wickthroughout the container (compare with FIG. 22). On the originalsidewall where the water was introduced, water wicked beyond the flapscore onto the top flaps (as denoted by the red line). Water alsocontinued to wick up onto the top flap.

This example shows that the Low-Wicking Medium container does not “pull”water into the container much above the level of the standing pool ofwater it may be in. On the other hand, the Control Medium container,when exposed to a constant source of free water, continues to “pull”that water into the container structure until equilibrium is reached(i.e., when the container structure completely saturated). There is amaximum amount of water, which will produce container failure regardlessof the paper combination used in an encapsulated container.

EXAMPLE 5 Wicking Testing for Encapsulated Containers

In conjunction with Example 4, a second trial was conducted with samplecontainers from the same materials as those described in Example 4. Inthis example, ten containers of each of the two medium types (Controland Low-Wicking Mediums) were placed in a standing pool of water. Eachcontainer stood in approximately 1 inch of water. The pool wascontinually fed a small stream of water to maintain a constant depth.Each container had a hole intentionally created in a bottom corner withsandpaper, not at the manufacturing joint. All of the containers wereweighted from above to keep them in the water and prevent floating.

After three plus days, five containers of each type were removed fromthe pool with the intention of doing top-to-bottom compression testing.However, all the containers were so wetted out on the bottom that doingtop-to-bottom tests was infeasible. Upon removing the containers fromthe pool, observations were made about the different wetness areas. Inthat regard, the containers having the Low-Wick Medium were completelysaturated on all the bottom flaps and approximately 1 to 1.5 inches upall the sidewalls. These containers only minimally wicked water abovethe level of the pool, which is consistent with the results described inthe previous examples.

Of the five Control Medium samples, the bottom flaps on all of thesecontainers were completely saturated as well. In addition, water wickedup to a minimum of 3 inches on all panels with a majority of the panelshaving water halfway or more up the sidewalls of the panels.

The other ten samples (five of each type of medium—Control and Low-Wick)were allowed to soak for three additional days. The Low-Wick Mediumsamples had no further take up of water beyond 0.5 inch level above thelevel of the pool. The remaining Control Medium containers continued towick all the way up the sidewall and onto the top flaps of thecontainers.

EXAMPLE 6 Compression and Water Take-Up Testing for EncapsulatedContainers

Ten samples of the encapsulated broccoli container containing 36#Low-Wick Medium (Spec. No. 4491) and ten sample containers containing36# Control Medium (Spec. No. 4490) were subjected to testing. Holeswere formed in two bottom corners of each container. Each container wasthen filled with 35 pounds of roll cores which were enclosed in aplastic bag, and the containers were closed. Each set of ten containerswas then stacked on its own pallet. Three layers were built using fourcontainers on the bottom and middle layers and two containers on the toplayer. The two pallets were placed directly underneath their own sprayhead.

Initially, each container was hand watered, using a garden hose tosimulate the initial soaking a container would receive in a spray or aclamshell applicator. Then, the spray nozzles were turned on at acontrolled rate of 0.14 gallons/minute. The containers were left forseven days under the shower.

The containers were emptied of the roll cores and taken to the lab fortop-to-bottom compression testing. Table 2 displays the results of thecompression testing. TABLE 2 COMPRESSION TEST RESULTS Control LowWicking Dry Medium Medium Container Peak Force Avg. (lbf) 281.2 787.51050 Std. Deviation 161.5067 75.5561 — Minimum 64 612 — Maximum 550 867— Peak Displacement Avg. 0.138 0.195 — Std. Deviation 0.05474 0.02377 —

Dry containers were also tested to compare to the watered containers andaveraged 1050 pounds force average. Therefore, the containers withLow-Wick Medium lost an average 25% of their top-to-bottom strength,while the containers with Control Medium lost 73% of their top-to-bottomstrength.

The differences between the two types of container were even moreapparent when the containers were handled. The containers with ControlMedium were almost entirely soaked. All panels were partially, if notcompletely wet. The containers with Low-Wick Medium had only small areasof wetness, with the exception of one container, which had some largerareas of wetness. In the one exception container, water had penetratedother holes that were in the container prior to the test and had notbeen made as a uniform testing condition. Due to the Low-Wick Medium,however, the water that entered these holes also did not spread throughthe entire panel of the container. The data in Table 2 shows thedifferences in water take-up in grams on average. TABLE 3 WATER TAKE-UPControl Low Wicking Dry Medium Medium Container Water Absorbed Avg. (g)320.23 41.3 0 Std. Deviation 131.93684 58.39825 — Minimum 149.2 13.3 —Maximum 545.4 198.1 —

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the disclosure.

1. A cellulose based substrate, comprising: (a) a cellulose based sheethaving a corrugated medium spanning between first and secondlinerboards, wherein the corrugated medium includes at least one sizingagent for moisture wicking resistance; and (b) a polymeric filmencapsulating at least a portion of the cellulose based sheet.
 2. Thecellulose based substrate of claim 1, wherein the at least one sizingagent includes alum for sizing the natural resins of the cellulose. 3.The cellulose based substrate of claim 1, wherein the at least onesizing agent includes a reactive sizing additive.
 4. The cellulose basedsubstrate of claim 1, wherein the at least one sizing agent is areactive sizing agent selected from the group consisting of alkyl ketenedimer, alkenyl ketene dimer emulsion, alkenyl succinic anhydride (ASA),and any blends thereof.
 5. The cellulose based substrate of claim 4,wherein the reactive sizing agent is present in the corrugated medium inan amount within the range of about 0.1 to about 4.0 lb/ton.
 6. Thecellulose based substrate of claim 1, wherein the corrugated mediumfurther includes a cationic crosslinking-type wet strength resin.
 7. Thecellulose based substrate of claim 6, wherein the resin is selected fromthe group consisting of urea-formaldehyde condensation products,melamine-urea-formaldehyde condensation products, andpolyamide-epichlorohydrin reaction products.
 8. The cellulose basedsubstrate of claim 1, wherein the corrugated medium includes about 0 toabout 30% virgin cellulosic fiber.
 9. The cellulose based substrate ofclaim 1, wherein the polymeric film encapsulating at least a portion ofthe cellulose based sheet is adhesively bonded to the first and secondlinerboards.
 10. The cellulose based substrate of claim 1, whereincorrugated medium spanning between first and second linerboards isbonded to the first and second linerboards using a water-resistantadhesive.
 11. A container, comprising: (a) a cellulose based sheethaving a corrugated medium spanning between first and secondlinerboards, wherein the corrugated medium includes at least one sizingagent for moisture wicking resistance; and (b) a polymeric filmencapsulating at least a portion of the cellulose based sheet.
 12. Acontainer, comprising: (a) a cellulose based sheet having a corrugatedmedium spanning between first and second linerboards, wherein thecorrugated medium includes a sizing agent for moisture wickingresistance and a reactive cationic cross-linking type resin for improvedwet strength; and (b) a polymeric film encapsulating at least a portionof the cellulose based sheet.
 13. The container of claim 12, wherein thesizing agent is alum for sizing the natural resins of the cellulose. 14.The container of claim 12, wherein the sizing agent is a reactive sizingagent selected from the group consisting of alkyl ketene dimer, alkenylketene dimer emulsion, alkenyl succinic anhydride (ASA), and any blendsthereof.
 15. The container of claim 14, wherein the reactive sizingagent is present in the corrugated medium in an amount in the range ofabout 0.1 to about 4.0 lb/ton.
 16. The container of claim 12, whereinthe corrugated medium includes about 0 to about 30% virgin cellulosicfiber.
 17. The container of claim 12, wherein corrugated medium spanningbetween first and second linerboards is bonded to the first and secondlinerboards using a water-resistant adhesive.
 18. The container of claim12, wherein the polymeric film encapsulating at least a portion of thecellulose based sheet is adhesively bonded to the first and secondlinerboards.